Conventionally, there is a seat device including airbags arranged below the seat seating surface and an internal pressure control unit for controlling the internal pressure of the airbags. For example, a seat device described in Patent Document 1 includes a pair of airbags, which is located at positions corresponding to the left buttock and the right buttock of the occupant seated on the seat seating surface. The internal pressure control unit is adapted to expand and contract the airbags alternately.
In this configuration, the buttocks of the occupant, which are supported above the airbags, are allowed to simulate walking movement. The seat device thus stimulates the muscles of the lower limbs of the occupant and promotes blood circulation, thus decreasing fatigue of the occupant.
A seat device described in Patent Document 2 detects seating of an occupant on a seat seating surface based on change of internal pressure of airbags. After detection of such seating, the seat device controls the internal pressure of the airbags to the target value.
A seat device described in Patent Document 3 detects the body size of an occupant seated on a seat seating surface through pressure detection. Based on the detected body size, the seat device executes internal pressure control on airbags.